The present invention relates to tumbling apparatus, and is particularly well suited for use in drum blast apparatus, i.e., tumbling apparatus used in combination with abrasive blasting equipment.
It has been known for some time to use various endless conveyors to tumble workpieces in a mill. Typical devices are disclosed in U.S. Pat. No. 1,833,301 to L. D. Peik and U.S. Pat. No. 3,585,758 to Willard J. Harper. These devices relate to conveyors made of segmented links, which are usually made of metal.
More recently, the art has recognized the utility of elastomer belts, such as disclosed in U.S. Pat. No. 3,715,840 to Davidson. In the Davidson patent an elastomer belt is driven to provide a tumbling effect; however, the tension on the belt is adjusted to support workpieces without requiring any additional underlying support during tumbling. Although a V-shaped belt guide is provided underneath the belt, the patentee teaches that the belt is ideally not in contact with the belt guide while in operation.
It is known to support elastomer tumbling belts by providing resiliently coated support idler rollers underneath the weight-bearing portion of the driven belt. It has been necessary to provide the resilient coating on these idler support rollers to prevent the metal support roller from acting as an anvil. Without the coating, the falling workpieces cause pinching and cutting of the belt vastly decreasing its useful life. Furthermore, it has been found that a multiplicity of resiliently coated idler support rollers are required to give the necessary support along an adequate length of the belt. The resiliently coated idler support rollers are expensive and multiples of them greatly add to the cost of conventional apparatus.
Accordingly, it can be seen that there is a need in the art for an easily constructed, inexpensive drum blast apparatus having a support for a main driven elastomer belt, which does not cause pinching or cutting of the main belt, and which does not unduly add to the expense of the apparatus.